I think the discussion on Reddit you're referring to was saying something slightly more nuanced than that. The case I specifically remember was someone arguing

I think the discussion on Reddit you're referring to was saying something slightly more nuanced than that. The case I specifically remember was someone arguing that simply passing through a C library function call without making it clear certain invariants needed to be held in the calling Rust code to not cause undefined behavior was somehow "safe". If you're wrapping a C call with some Rust code and you don't ensure all the invariants that could crash the C code are taken care of, then your function is still unsafe. If you do ensure that all the invariants are taken care of that could crash the C code are taken care of, then it's fine to have it be safe.